Well casing protector method



WELL CASING PROTECTOR METHOD 4 Doyne L. Wilson, Pasadena, Calif., assignor to on Base, vInc., Compton, Calif., a corporation of California No Drawing.. Application February 9, 1953,

Serial No. 336,007

1 Claim. (Cl. 1661) This invention relates to the protection of oil, gas and water well casing, and has particular reference to well casing protector compositions and to methods for use of the same.

The steel casing or pipe which is left in a drilled well is subject, in some areas, to severe corrosion and to serious deformation or even complete shearing due to lateral movement of strata in earthquake zones. One of the principal objects of this invention is to provide compositions particularly adapted for use in protecting well casings from corrosive environments and from the destructive influence of sub-surface movement.

The factors which promote sub-surface casing corrosion are multiple and complex. In Kansas, the most serious corrosion problems are caused by the so-called Dakota waters which have been shown to have pronounced lateral, and some vertical, sub-surface movement. In West Texas and in New Mexico, sour crudes, which are rich in hydrogen sulfide, are chiefly responsible for sub-surface corrosion. In other areas such as, for example, Ventura, California, severe corrosion occurs due primarily to the action of anaerobic sulfate reducing bacteria. It is thus apparent that the physical properties of compositions for use in anticorrosion programs must vary to a great extent and this is particularly true of properties such as gel strength, fluidity, weight, temperature stability and fluid loss. Another important object of this invention is to provide a basic anticorrosion composition which meets these requirements and which may be adapted to be used against widely different types of corrosive environments.

Casing deformation and shearing due to lateral movement of certain strata in an earthquake Zone is caused by transmission of the shock by the formation which is in direct contact with the casing. Casing corrosion also results from a direct contact with the casing well, in this case by the particular corrosive medium. Another object of this invention is, therefore, to provide compositions which may be placed into contact with the exterior wall of the casing to insulate and protect it from the harmful effects of sub-surface movement and sub-surface corrosion.

Another object of this invention is to provide compositions, of the type broadly described above, which are relatively inexpensive and easily applied at the well site.

Other objects and advantages of this invention it is believed will be readily apparent from the following detailed description of preferred embodiments thereof.

Briefly, this invention comprises the discovery that the properties of a base oil may be modified to suit it for use in anticorrosion and other casing protection applications. In earthquake protection applications, the annulus surrounding the casing is enlarged and filled with the modifiedoil composition which sets to a plastic gel, the composition completely covering the casing well to act as a barrier to prevent corrosive mediums from contacting the c asin gQL The plastic gel is sufliciently rigid, at the temperature of the zone, to support any sloughing from the wall of the hole, and sutficien'tly plastic to absorb the ferred embodiment of this invention but it is not intended 2,773,550 Patented Dec. 11, 1 956 shock of an earth movement without transmitting it to the pipe. The composition is further. characterized by a very low loss of fluid to the surrounding earthen formation. Base oils which have been found to'be suitable in the compositions of this invention include, but are not limited to: toppedcrudes, road oils, residual oils, heavy crudes and tars, all thinned as and if required with less viscous oils such as gas oil, stove oil, diesel oil, naphthas, kerosenes, cracked distillates, aromatics, etc.

The following specific example is illustrative of a preto limit the invention thereto.

Phase I Bunker C fuel oil bbls 221 Water bbls 11.3 Caustic solution (50% by weight) lbs 1316 Phase II Bunker C fuel oil bbls- 81 Fatty acid lbs 1974 Weight material (98% through 325 mesh) lbs 5593 The caustic of the above example was soditun hydroxide, but it will be understood that other alkali metal hydroxide, such as potassium hydroxide, may be used. The fatty acid used was Vopcolene 58, an hydrogenated tallow fatty acid having 16-18 carbon atoms. Fatty acids within the scope of this invention comprise those having 12-18 carbon atoms, and which may be represented by the general formula CHa(CHz)1tCOOH,- where n: 10-16. Such fatty acids include lauric, tridecoic, myristic, pentadecoic, palmitic, margaric and stearic.

The weight material of the example was ground limestone. Other materials such as, for example, barytes, crushed oyster shells, etc., may also be used, as will be readily apparent to those skilled in the art.

In use, Phase I and Phase II were "both produced by mechanical agitation, the oil having been heated to approximately 190 F. By means of pumps the two phases thus produced were blended in an approximate ratio of Phase IzPhase 11:22.5:1 to produce a thixotropic gel. The blend was pumped down the drill pipe, through a port collar in the casing, and up the annulus between the casing and the wall of the hole, wherein it set up as a gel. It is generally necessary, in the case of earthquake protection applications at least, to enlarge the annulus before application in order to make certain that the pipe or casing is fully covered with the protector composition. An increase of about three times the normal diameter has been found to be adequate.

Protector compositions of this invention have a grease cone penetration in the range of 150-400, the particular gel strength, with a given base oil being dependent upon the acid and caustic concentration. This penetration test is described in ASTM DesignationzD217-44T, and involves the use of a grease cone penetrometer, the unworked consistency of the sample being determined therewith after standing for twenty-four hours at a temperature of ::1" F. The results are expressed in terms of tenths of a millimeter of penetration.

The proportions of ingredients in the casing protector composition'of this invention may be varied within the following critical limits per barrel of total composition:

(a) With less than 10 pounds of water per barrel:

Pounds Fatty acid 3-6 Sodium hydroxide 1-2 (b) With 10-35 pounds of water per barrel:

Pounds Fatty acid 5-6 Sodium hydroxide 1-2 be'illustrative only. Any modification of or variation therefrom which conforms to the spirit of the invention is intended to be included within the scope of the claim.

I claim.

A process for protecting well casings from sub-surface shock and corrosion, comprising the steps of forming an annulus between the well casing and the surrounding earthen formation, and applying to said annulus, to fill the same, a thixotropic composition prepared by dispersing in a base oil about 3 to about 6 pounds per barrel of a fatty acid having 12 to 18 carbon atoms per molecule, from about 1 to 2 pounds per barrel of an alkali metal hydroxide, a weight material, and water, said composition having'a grease-cone penetration. after standing for 24 hours at 120:1 F. in the range of from 150 to 400 millimeters/ 1O.

References Cited in the file of this patent UNITED STATES PATENTS Cooper Dec. 13, Saye Apr. 21, Hilliker Jan. 29, Kaufman May 28, Hilliker July 13, Adams et al Jan. 21, Gothard et al. June 17, Brunstrum Sept. 9, Lerch et al. May 16, Swenson July 4, OHalloran et al. Mar. 4, Fischer May 18, 

